On 7/12/2022, Rohith Kollalsi wrote:
> According to the programming guide, it is recommended to
> perform a GCTL_CORE_SOFTRESET only when switching the mode
> from device to host or host to device. However, it is found
> that during bootup when __dwc3_set_mode() is called for the
> first time, GCTL_CORESOFTRESET is done with suspendable bit(BIT 17)
> of DWC3_GUSB3PIPECTL set. This some times leads to issues
> like controller going into bad state and controller registers
> reading value zero. Until GCTL_CORESOFTRESET is done and
> run/stop bit is set core initialization is not complete.
> Setting suspendable bit of DWC3_GUSB3PIPECTL and then
> performing GCTL_CORESOFTRESET is therefore not recommended.
> Avoid this by only performing the reset if current_dr_role is set,
> that is, when doing subsequent role switching.
>
> Fixes: f88359e1588b ("usb: dwc3: core: Do core softreset when switch mode")
> Signed-off-by: Rohith Kollalsi <quic_rkollals@xxxxxxxxxxx>
> ---
> drivers/usb/dwc3/core.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 050b2ba5986d..7ce0e033d755 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -158,9 +158,13 @@ static void __dwc3_set_mode(struct work_struct *work)
> break;
> }
>
> - /* For DRD host or device mode only */
> - if ((DWC3_IP_IS(DWC3) || DWC3_VER_IS_PRIOR(DWC31, 190A)) &&
> - dwc->desired_dr_role != DWC3_GCTL_PRTCAP_OTG) {
> + /*
> + * When current_dr_role is zero, do not perform GCTL_CORESOFTRESET.
The line above doesn't really explain why. Can you rephrase it to
something like this or the equivalent:
"When current_dr_role is not set, there's no role switching. Only
perform GCTL.CoreSoftReset when there's DRD role switching."
Thanks,
Thinh
> + * Perform it only for DRD host or device mode.
> + */
> + if (dwc->current_dr_role && ((DWC3_IP_IS(DWC3) ||
> + DWC3_VER_IS_PRIOR(DWC31, 190A)) &&
> + dwc->desired_dr_role != DWC3_GCTL_PRTCAP_OTG)) {
> reg = dwc3_readl(dwc->regs, DWC3_GCTL);
> reg |= DWC3_GCTL_CORESOFTRESET;
> dwc3_writel(dwc->regs, DWC3_GCTL, reg);
